The subject invention relates to a circuit board misalignment detection apparatus, and in particular, to a non-contact misalignment detection apparatus.
The following methods for correcting misalignment between a circuit board and an inspection jig in a printed circuit board inspection apparatus are commonly known.
A first method is to photograph a reference point on the circuit board in order to detect misalignment (Japanese Patent Application Laid Open No. 1-184473, etc.) A second is to provide on an inspection jig a probe for detecting misalignment while forming a corresponding reference pattern on the circuit board (Japanese Patent Application Load Open NO. 6-51013).
These misalignment detection methods have the following problems. The first method requires an expensive camera and substantial time to install and remove the camera. In addition, a mark for the camera must be formed on the circuit board, and certain circuit boards do not allow such a mark to be provided near the position at which the camera is stopped.
The second method requires a special pattern on the circuit board for detecting misalignment. Furthermore, since a probe and the pattern must be electrically connected together, it is cumbersome to remove resists formed on the pattern.
It is a general object of the subject invention to provide a misalignment detection apparatus and method that solves the foregoing problems and can easily detect misalignment in a non-contact manner using a simple structure.
According to the circuit board misalignment detection apparatus of the present invention, misalignment is detected based on the variation in electrostatic capacity depending on the opposition condition between the wiring on an inspected circuit board and an electrode provided opposite the wiring. Thus, misalignment can be detected so long as the electrostatic capacity between the wiring and the electrode can be detected. That is, the apparatus does not require a camera or a special mark to be formed on the inspected circuit board, as in the prior art. Furthermore, common hardware can be used in an inspection apparatus for conducting continuity and short-circuit test based on electrostatic capacity.
More particularly, an electrostatic capacity detection means monitors variation in electrostatic capacity depending on the opposition condition between the electrode and the wiring, and a determination means reads the misalignment based on the detected electrostatic capacity. Thus, the apparatus neither requires a camera or a special mark on the inspected circuit board, as in the prior art. Furthermore, as above, common hardware can be used in the inspection apparatus for conducting a continuity and short-circuit test based on the electrostatic capacity.
Further, the circuit board misalignment detection apparatus has first and second X-direction electrodes for detecting misalignment in the X direction. It also has first and second Y-direction electrodes for detecting misalignment in the Y direction. Thus, the direction of misalignment can be detected to allow prompt correction.
Still further, first and second x-direction electrodes are disposed so as to be point-symmetrical relative to an arbitrary point on a line that extends approximately along the center of the wiring on the opposite circuit board and is parallel with the Y axis. The first and second Y-direction electrodes are disposed so as to be point-symmetrical relative to an arbitrary point on a line that extends approximately along the center of the wiring on the opposite circuit board and is parallel with the X axis. Thus, misalignment can be reliably detected in both the X and Y directions.
Still further, the first and second X-direction electrodes partly protrude from the wiring of the opposite circuit board even if there is no misalignment in the X direction. Similarly, the first and second Y-direction electrodes partly protrude from the wiring of the opposite circuit board even if there is no misalignment in the Y direction. Thus, misalignment can be detected even if the wiring for which misalignment is to be detected is of minimal cross section.
Still further, the apparatus preferably has two sets of X- and Y-direction electrodes, and the determination means reads the misalignment in the xcex8 direction based on the electrostatic capacity detected by the two sets of electrodes. Thus, misalignment can be detected in not only the X and Y directions, but also in the "THgr" direction.
Finally, the method for detecting misalignment between an inspected circuit board and a circuit board inspection apparatus, detects misalignment based on the variation in electrostatic capacity depending on the opposition condition between wiring on an inspected circuit board and an electrode provided opposite condition between wiring on an inspected circuit board and an electrode provided opposite to the wiring. Thus, misalignment can be detected as long as the electrostatic capacity between the wiring the electrode can be detected. That is, apparatus employing the method does not require the use of a camera or and as stated, a special mark on the inspected circuit board, as in the prior art. Furthermore and as stated, common hardware can be used for an inspection apparatus conducting a continuity and short-circuit test based on electrostatic capacity.